The invention relates to petrochemistry, and more particularly it relates to methods of dimerization of olefins. Olefins obtained by the herein-proposed method can be used as monomers and comonomers in the manufacture of polyolefins, as intermediates in the manufacture of monomers for synthesizing rubber, etc.
Known in the art are methods for dimerization of olefins by mixing them with various catalysts of the homogeneous or heterogeneous type.
Homogeneous catalysts consisting of an organoaluminum compound and a compound of a transition metal with low-molecular ligands, containing the elements standing in the V or IV groups of the Periodic Table (nitrogen, oxygen, phosphorus, sulphur) have certain disadvantages. The main drawback is the difficulty of isolation of the target products in their pure state, since special methods are required to separate the components that are present in one phase, and also the difficulty of performing the continuous process. As a rule, all methods are batch processes. Moreover, homogeneous catalysts are relatively unstable in time and cannot be recovered.
Dimerization of olefins with heterogeneous catalysts can be both batch and continuous processes. But as the reaction mixture is stirred in the process, or otherwise handled, heterogeneous catalysts become crushed and much of it is lost.
Furthermore, known homogeneous and heterogeneous catalysts fail to give high yields of butene-1 by dimerizing ethylene. (cis- and trans-butene-2, having a concentration of 85 to 98 per cent, are mainly produced). It is not possible to obtain high yields of methylpentenes in dimerization of propylene either (the methylpentene content of the dimerizate is 69 per cent maximum).
Known at the present time is the method of dimerization of olefins, having not over 12 carbon atoms, consisting in mixing at least one of said olefins with a two-component catalyst, consisting of an organoaluminum compound, having the general formula R.sub.n AlX.sub.3-n, where R is an alkyl having not more than 12 carbon atoms, X is a halogen, and n is 1 or 2; and a copolymer of vinylpyridine with a polyvinyl-substituted aromatic compound (e.g. divinylbenzene, trivinylbenzene), said copolymer containing 75 to 90 per cent by weight of polyvinylpyridine fragments that complexed with a nickel salt of an organic or a mineral acid; the molar ratio of the organoaluminum compound to the nickel salt is 1 - 100. Said olefins and said two-component catalyst are mixed in a medium of hydrocarbon or halocarbon solvents at a temperature of -50.degree. to +150.degree. C and a pressure of 1 to 100 atmospheres.
The catalyst used in this method (which is insoluble in the reaction medium) is characterized by the same disadvantages that are inherent in the known heterogeneous catalysts.